Electrostatic applying and holding device



May 13, 1958 J. o. TAYLOR ET AL 2,834,132

ELECTROSTATIC APPLYING AND HOLDING DEVICE Filed Dec. 14. 1954Sheets-Sheet 1 04K j/mu/m flit. 0014/4.

INVENTORS May 13, 1958 J. o. TAYLOR ET AL ELECTROSTATIC APPLYING ANDHOLDING DEVICE 2 Sheets-Sheet 2 Filed Dec. 14.

ATTORNEYZ United States Patent ELECTROSTATIC APPLYING AND HOLDING DEVICEJohn 0. Taylor, Pleasantville, and Ralph R. Bergman, New York, N. Y.,assignors, by mesne assignments, to American Type Founders Co., Inc.,Elizabeth, N. 1., a corporation of Delaware Application December 14,1954, Serial No. 475,195

Claims. (CI. 40-125) This invention relates to new and improvedapparatus for holding sheet material upon a supporting surface.

A principal object of this invention is to improve the smoothness ofdisplay of sheet materials.

Another object is to minimize the manual effort usually required inproviding for a smooth display of sheet materials having a relativelylarge area.

Another object is to eliminate the mechanical and physical disfigurementof sheet material incurred during holding.

Another object is to provide a versatile sheeet applying and holdingdevice capable of holding a sheet in any desired position with respectto a backing surface.

Heretofore most structures designed for holding sheet material in adesired fixed position with respect to a supporting surface havefeatured mechanical or adhesive arrangements. Many structures operativein accordance with these techniques have been unsatisfactory for thereason that it has been impossible to display or hold sheets having arelatively large area in a manner free from wrinkles and creases.

Electrostatic principles have also been applied in certain industrialapplications for the purpose of holding sheet material in a desiredposition upon conveyor belts and other movable structure. In theseapplications, the necessary potentials are usually generated by thefriction of moving components with a resulting attraction between acharged sheet and a conveyor belt or the like. Notwithstanding the factthat the application of electrostatic principles to sheet holdersresults in an advantageous mode of operation wherein large sheets may bedisplayed in a desired position completely free from creases andwrinkles, no one has heretofore suggested that these principles may beadvantageously applied to a display board type sheet holder, and withouta movement of components to generate a holding potential by friction.

In a preferred embodiment of this invention, a relatively fiat displayboard is utilized to support sheet material on one surface thereof. Froma generic aspect, however, the supporting surface of the board may beformed so as to have a surface of considerable contour. With eitherconstruction, the sheet will be held with a minimum of unwanted wrinklesand creases. The purpose for which the sheet is to be supported is notmaterial to this invention, and it may well be that the sheet is to beheld for exposure such as may be required in photography, or for visualdisplay, or so that information may be sketched or written thereon. Inany event, with the application of the structure of this invention to adisplay board, it is possible to hold the sheet in any desired positionrelative to the surface of the board without the use of mechanicalholding means such as clamps, thumb tacks, etc., and without the use ofadhesives such as glue or paste.

This mode of operation is obtained herein by enclosing within thedisplay board a relatively flat, sheet-like electrode generally parallelto the supporting surface of the board. Inasmuch as a relatively highvoltage is to be connected to this electrode sheet during the holdingop- ,7 2,834,132 Patented May 13, 1958 eration, the sheet supportingsurface of the display board is formed of an insulating sheet of plasticor the like. The sheet which is to be held is manually placed upon thesupporting surface of the board and is subjected to an electrostaticfield of exceedingly high intensity by applying a potential to theexposed surface thereof by means of an electroconducting roller or thelike. By continually rolling the energized roller over the surface ofthe sheet so that all areas thereof have been subjected to a relativelyhigh electrostatic intensity, electrostatic attraction causes the sheetto adhere to the display board in a manner free from all wrinkles andcreases and without necessity of mechanical or adhesive holding means.

In order that the structural features for attaining the objects of thisinvention may be readily understood, reference is herein made to theaccompanying drawings wherein:

Figure l is a simplified diagrammatic representation of the basicstructure employed in the electrostatic sheet applying and holdingdevice of this invention;

Figure 2 is a schematic diagram of the electrical circuitry employed ina preferred commercial embodiment of this invention;

Figure 3 is a partially broken-away view of a highvoltage, roller-typeapplicator for applying an electrostatic charge to a sheet which is tobe held;

Figure 4 is an end view of the applicator shown in Figure 3 with theroller guard cover in the safety position;

Figure 5 is a sectional view taken along line 5-5 of Figure 3 andshowing the application of the roller type applicator to a sheet mountedon a display board shown in section;

Figure 6 is a sectional view taken along line 6-6 of Figure 3 andshowing the roller guard cover in both the safety and operate positions;and

Figure 7 is a sectional view taken along line 7-7 of Figure 3 andshowing the roller guard cover in the safety position.

Referring now to Figure 1, the basic elements of the electrostatic sheetapplying and holding device of this invention comprise a high voltageenergizing source 10, a display board 11, and an applicator 12. Theinput terminals of source 10 will in most installations be energizedfrom a commercial volt alternating-current distribution line. Thehigh-voltage output of source 10 is a direct-current potential of theorder of several thousands of volts. The potential of one of thehigh-voltage output terminals is applied by conductor 14 to a sheet-likemetallic electrode 46 (shown in Figure 5) positioned within or on thebackside of display board 11 so as to be in a parallel plane withrespect to sheet 13 which is to be held in a fixed position with respectto display board 11. The other high-voltage output terminal of source 10is connected to a roller type applicator 12 by means of conductor 15. Ahigh-voltage circuit path is provided within roller type applicator 12as will be hereinafter explained in detail so that the surface of theroller assumes the high-voltage potential of conductor 15. If sheet 13is manually held in the desired position upon display board 11 andapplicator 12 is manually moved over the surface of sheet 13, theintense electrostatic field generated between applicator 12 and theelectrode connected to conductor 14 will cause sheet 13 to adhere to thedisplay surface of board 12 by electrostatic attraction in a manner freefrom all wrinkles and creases.

The amplitude of the direct-current output potential of source 10necessary to effectuate optimum holding will vary in differentsituations. In the main, the magnitude of this potential is dependentupon the thickness and dielectric constant of sheet 13 and the thicknessand 3 dielectric nstan f h ula in surf ce f, splay board 11 upon whichsheet 13 is held. In any event, the optimum minimum potential for highvoltage source may be readily determined by attempting to hold a sheetin place while working through a range of output potentials. In view ofthe high voltage employed it may be readily appreciated that the lowestvoltage satisfactory for proper holding is desirable from a safetyaspect.

In Figure 2, push-button type switch 16 and a solenoid 18 have beenadded to the circuitry to provide a commercial embodiment of the basicstructure shown in Figure 1. Push-button switch 16 is advantageouslylocated on the handle of roller type applicator 12 and is electricallyconnected in the input circuitry of high volt; age source 10 so thatmanual depression of the switch is required to close the energizationcircuit from the 110 volt A. C. line terminals through conductor 21,closed push-button switch 16, conductor 24, input of high voltage source10, conductor 20 and conductor 19 to the line source. In the event highvoltage source It) incorporates a filament type rectifier tube and afilter circuit having a relatively long time constant, some delay willbe introduced in the time interval within which output will appear fromhigh voltage source 10 after the depression of push-button switch 16.Should this delay be objectionable, a high voltage relay may beincorporated in the output circuitry of high voltage source It), andpushbutton switch 16 may be connected to a low voltage energizing coilfor this relay. With this arrangement, filament heating and capacitorcharging delays will be eliminated. However, the high voltage supplywill be energized at all times and an additional switch will be requiredto deenergize sourcelt).

In a preferred construction for roller type applicator 12, roller 34 isenclosed within a metallic safety housing. This housing comprises amovable cover portion which is withdrawn by energizing toroidal solenoid17 by'current flow in a circuit which includes conductor 21 closedswitch 16, conductor 22, the winding of solenoid 17, con? ductor 23.andconductor 19. Armature 18 is rotatably moved in response to theenergization of solenoidgl7, and as will be hereinafter described indetail this armature movement is translated into a correspondingmovement of the safety cover for applicator 12. Accordingly, thedepression of switch 16 energizes high voltage source 10 and therebyapplies high voltage to applicator 12 and the electrode of display board11, and also eflectuates the withdrawal of the safety cover forapplicator 12.

Referring now to Figures 3 through '7, high voltage applicator 12comprises a cylindrical roller 34 supported at the terminal ends thereofby trunnions 36m and 361') which matewith bearings 38a and 38b,respectively. The bearings are fabricated of any conventional insulatingmaterial suitable for withstanding relatively igh Voltages. -Roller 34is housed within protective metallic covering structure comprisingrollerguard 32' and roller guard extension 33. Each bearing 38a and 38bincludes a flatbase portion which is screwed to the associated end wallportion of roller guard 32 and theprojectingfiange portionsof bracket 31by means of screws 43.

The cylindrical surface 35 of roller 34 is processed with an.electroconducting film which may be, aquadag or silver paint, and theright-hand portion of roller. 34 is also processed with a correspondingconducting film whereby trunnion 36b is, electrically connected to thecylindrical surface 35 of roller 34. 7 Metallic slip ring 37 'is formedwithin bearing 38b and establishes a friction electrical contact withtrunnion 36b. High voltage conductor 15'is soldered or otherwiseconnected to'the projecting lug of slip ring 37 and is clamped to thebottommost portion of roller guard 32 by means of clamps 44. Grommet 40insulates high-voltage conductor 15 from roller guard 32, and the cableis fed through an axial hole located within handle 30. Grommet 39insulates conductor 15 from metallic support bracket 31.

The terminal ends of roller guard extension 33 are formed with flanges41a and 41b which bear against the base portion of bearings 38a and 38b,respectively. This coupling arrangement enables roller guard extension33 to be relatively movable with respect to roller guard 32 wherebyroller 34 may be partially exposed or fully enclosedby the protectivemetallic housing as desired. An exposed view of the roller is shown inFigure 5.

Toroidal solenoid 17 is fixedly positioned upon the projecting portionof roller support bearing 38;: and the motion of the movable armature 18is transmitted to roller guard extension 33 by means of connector 42.With such an arrangement, the energization of solenoid 17 causes, thewithdrawal of roller guard extension 33 at the desired times inresponseto the manual depression of push-button switch 16. Biasing springs (notshown) force armature 18 in a position which will cause roller guardextension 33 to envelop roller 34 whenever pushbutton switch 16 is inthe open position. Figures 4, 6 and 7show the roller applicator 12 inthe safety position in which guard extension 33 and guard 32 fullyenclose roller 34. Figure 5 and the broken line positioning ofcomponents in Figure 6 show guard extension 33 in the withdrawnposition.

The detailed construction of a preferred embodin en of a display board11 is shown in Figure 5. The display board comprises a front cover 45constructed of insulating material and a back cover 47 also constructedof insulating material. Metallic sheet 46 is fixedly positioned withinthebox-like display board structure and conductor 14 provides anelectrical path to electrode 46 from the high voltage source. As isshown in Figure 5, with roller guard extension 33 withdrawn in responseto the energization of solenoid 17, the electroconducting Coating 35 ofroller 34 creates a relatively intense electrostatic field in theshortest straight line distance between film 35 and electrode 46 wherebyelectrostatic attraction causes sheet 13 to adhere to the front section45'of display-board 11. By manually moving applicator 12 over allsurface portions of sheet 13 electrostatic attraction causes sheet 13 toadhere smoothly and firmly upon the front section of display board 11without wrinkles and creases.

It is to be understood that the above-describedarrangements areillustrative of theapplications of the principles of this invention.Numerous other arrangements may be devised by those skilled in the artwithout departing from the scope of the invention Having thus describedthe invention, what is claimed as new and desired to be secured byLetters Patent is:

1. An electrostatic sheet applying and holding device comprising sheetholding means including a relatively smooth sheet supporting surface ofelectrical insulating material, a flat electrode supported on the back'of said sheet supporting surface, an instrument comprising an extendedcurrent carrying surface providing a second electrode, and a source athigh voltage current connected with said electrode whereby when a sheetis placed upon the sheet supporting surface, the sheet is charged whenthe instrument is. moved thereover and the sheetis sustained upon thesupporting surface by the electrostatic charge induced. onthe sheet. I

2. An electrostatic sheet applying and holding device in accordance withclaim 1 wherein said instrument has a cylindrical shape.

3. An electrostatic sheet applyingand holding'device according to claim2 where said instrument .is rotatably ounted,-

lectrosta c eet app yi an holdin devic comprising sheet holding meansincluding a relatively moo h he prortins f e t al insula m e -a tar lctrbde conformi g o the c nfi ur tion o nd. d sposed. adjacen o saisheet uppor in r ace. an instrument comprising a current carryingsurface providinga second electrode, and a source of highvoltageconnected between said electrodes whereby when a sheet is placed uponthe sheet supporting surface, the sheet is charged when the instrumentis moved thereover and the sheet is sustained upon the supportingsurface by the resulting electrostatic charge.

5. An electrostatic sheet applying and holding device in accordance withclaim 4, wherein said instrument comprises a cylindrical roller andadjustable guard means mounted adjacent the periphery of said roller.

References Cited in the file of this patent UNITED STATES PATENTSHutchinson July 29, 1913 Chamberlain Aug. 25, 1942 Walkup et al. Nov. 6,1951 Ebert Aug. 4, 1953 Mayo et a1. July 27, 1954 Butterfield NOV. 2,1954

